A method of dispersing a self-emulsifying crosslinker, the obtained crosslinker dispersion and its applicaton in e-coat having low baking temperature

Abstract

Disclosed herein is a method of dispersing a self-emulsifying crosslinker including at least two steps: i) preparing an aqueous acid dispersion (I) of a self-emulsifying crosslinker, and the microstructure of liquid phase of the aqueous acid dispersion (I) is water-in-oil; and ii) adding water into the aqueous acid dispersion (I) to obtain an aqueous acid dispersion (II), and the microstructure of liquid phase of the aqueous acid dispersion (II) is oil-in-water. Additionally disclosed here is a self-emulsifying crosslinker dispersion prepared by the method and the self-emulsifying crosslinker dispersion has a Z-average particle size in a range of from 50 to 200 nm.

1 . A method of dispersing a self-emulsifying crosslinker comprising at least two steps:
 i) preparing an aqueous acid dispersion (I) of a self-emulsifying crosslinker, wherein the microstructure of liquid phase of said aqueous acid dispersion (I) is water-in-oil; wherein a solid content of said aqueous acid dispersion (I) in step i) is from 45% to 75% by weight, based on the total weight of said aqueous acid dispersion (I); and   ii) adding water into said aqueous acid dispersion (I) to obtain an aqueous acid dispersion (II), wherein the microstructure of liquid phase of said aqueous acid dispersion (II) is oil-in-water; wherein a detected maximum temperature (T max ) of said aqueous acid dispersion (II) in step ii) is no more than 40° C.   
     
     
         2 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein said self-emulsifying crosslinker is at least one selected from the group consisting of cationic polyaromatic urethane, cationic polyaliphatic urethane, waterborne amino resin, cationic polyester polyurethane, cationic polyester polyurea, and cationic polycarbonate polyurethane. 
     
     
         3 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein in step i) said aqueous acid dispersion (I) is prepared by mixing the self-emulsifying crosslinker, acid and water under stirring at a rate in a range of from 500 to 2000 rpm and in step ii) said aqueous acid dispersion (II) is prepared under stirring at a rate in a range of from 200 to 1500 rpm. 
     
     
         4 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein the solid content of said aqueous acid dispersion (I) in step i) is from 50% to 70% by weight, based on the total weight of said aqueous acid dispersion (I). 
     
     
         5 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein the solid content of said aqueous acid dispersion (II) in step ii) is in a range of from 20% to 30% by weight, based on the total weight of said aqueous acid dispersion (II). 
     
     
         6 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein the detected maximum temperature (T max ) of said aqueous acid dispersion (II) in step ii) is no more than 30° C. 
     
     
         7 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein the acid used in step i) to prepare said aqueous acid dispersion (I) is at least one selected from the group consisting of diluted hydrochloric acid, diluted sulfuric acid, phosphoric acid, diluted nitric acid, boric acid, perchloric acid, formic acid, acetic acid, lactic acid, oxalic acid, glycolic acid, citric acid, malic acid, adipic acid, succinic acid, propionic acid, fumaric acid, and benzoic acid. 
     
     
         8 . The method of dispersing a self-emulsifying crosslinker according to  claim 1 , wherein the weight percentage of acid in said aqueous acid dispersion (I) is in a range of from 0.1 wt. % to 5.0 wt. %. 
     
     
         9 . A self-emulsifying crosslinker dispersion prepared by the method according to  claim 1 , wherein said self-emulsifying crosslinker dispersion has a Z-average particle size in a range of from 50 to 200 nm. 
     
     
         10 . The self-emulsifying crosslinker dispersion according to  claim 9 , wherein said self-emulsifying crosslinker dispersion has a PDI (Polydispersity Index) of less than 0.2. 
     
     
         11 . The self-emulsifying crosslinker dispersion according to  claim 9 , wherein solid content of said self-emulsifying crosslinker dispersion is in a range of from 20% to 30% by weight. 
     
     
         12 . The self-emulsifying crosslinker dispersion according to  claim 9 , wherein said self-emulsifying crosslinker dispersion comprising at least one selected from the group consisting of cationic polyaromatic urethane, cationic polyaliphatic urethane, waterborne amino resin, cationic polyester polyurethane, cationic polyester polyurea, and cationic polycarbonate polyurethane. 
     
     
         13 . An e-coat composition comprising at least one base resin dispersion and at least one self-emulsifying crosslinker dispersion according to  claim 9 . 
     
     
         14 . The e-coat composition according to  claim 13 , wherein said base resin is at least one selected from the group consisting of polyetheramine and polyetheramine-based epoxy resin. 
     
     
         15 . The e-coat composition according to  claim 13 , wherein said e-coat composition has a curing temperature in a range of from 80° C. to 140° C. 
     
     
         16 . An e-coat layer obtained from the e-coat composition according to  claim 13  after curing at a temperature in a range of from 80° C. to 140° C. 
     
     
         17 . A substrate coated with the e-coat layer according to  claim 16 . 
     
     
         18 . A self-emulsifying crosslinker dispersion prepared by the method according to  claim 1 , wherein said self-emulsifying crosslinker dispersion has a Z-average particle size in a range of from 60 to 160 nm. 
     
     
         19 . The self-emulsifying crosslinker dispersion according to  claim 9 , wherein said self-emulsifying crosslinker dispersion has a PDI (Polydispersity Index) of less than 0.1.